Known burners for a low energy product gas are designed to burn the low energy gas together with a high energy support fuel whereby the several fuels might achieve a predetermined output through the use of a multiple burner arrangement. In such a multiple burner arrangement, one or more burners thereof may be taken out of service at low loads to facilitate turndown, while under conditions calling for full load, all burners are pressed into maximum operation.
In a typical burner designed for low energy fuel, the entire amount of fuel and air required for complete combustion is mixed together and then directed through the throat of a burner, whereby the throat of the burner must be designed to carry the combined volume of fuel and combustion air. The volume of the low energy fuel used is frequently greater than the volume of air required to burn it, therefore a large burner throat is required. If the burner throat were made sufficiently large for low energy product gas, it would be oversized for high energy fuel, and it would be oversized for optimum flame stability when burning low energy gas under conditions of low load.